Rockstar Games have put up the Multiplayer Event listing for October to December 2011, even though it is mainly filled with Red Dead Redemption events, there are a few special Grand Theft Auto events listed:

Friday, October 21 (5-8PM Eastern)
Grand Theft Auto IV: Complete Edition (GTA Anniversary Celebration)
For PlayStation 3 on PSN10 years ago this weekend, Grand Theft Auto III was unleashed on the world. Join us for some all out GTA multiplayer mayhem in the streets of Liberty City to celebrate that game's anniversary and impact. Expect some very special Grand Theft Auto giveaways to mark the occasion - stay tuned for much more info...

Friday, December 2 (4-7PM Eastern)
Grand Theft Auto IV & Episodes from Liberty City
For PC on Games for Windows LIVEThree years to the day since the original release of GTAIV on the PC! PC gamers that got their first taste of GTA multiplayer with that release, please celebrate with us online with some up-to-32 player action in all the original modes as well as The Lost and Damned and The Ballad of Gay Tony. 20 Rockstar prize packs will be given away...

Very special Grand Theft Auto giveaways to mark the occasion of the 10 year anniversary of Grand Theft Auto III, sounds interesting, meanwhile they will also be marking the Grand Theft Auto IV PC anniversary with a few rounds on Multiplayer, so here's a video of what to expect: